1. Field of the Invention
The present invention relates to a method for determining the precipitation rate and reflectivity factor of a hydrometeor using pulsed radar operating at a wavelength which is attenuated by hydrometeors, and to a dual polarization meteorological radar implementing this method.
2. Discussion of the Background
In meteorology, it is necessary to observe rainfall and other hydrometeors, in particular for the purpose of short term forecasting. To this end, consideration has for a number of years been given to using radar for quantitatively determining the precipitation rate, this being a characteristic parameter of these phenomena. To do this, use is made of methods based on measuring the reflectivity of the rain or hydrometeors when illuminated with a radar beam. However, for most of these methods, attenuation by the hydrometeors biases the measurements, and it is therefore necessary to operate at wavelengths which are attenuated as little as possible, and are therefore relatively high. This leads to working difficulties and high cost.
Another, more attractive method has been proposed: that of attenuation for two wavelengths and a single polarization, and this has the advantage of being independent of the calibration of the radar. However, this method leads to certain technical difficulties in obtaining measurements with the required precision. This is because problems are encountered in making the beams at the two wavelengths coincide and in the measurements being simultaneous.
All the studies which have been carried out demonstrate the benefit of using radars with shorter wavelength, making it possible to choose more compact and less expensive equipment. However, this would entail problems of correcting attenuation which are very difficult to solve, in particular when there is heavy precipitation.